The One Direction star decided to interrupt an interview with 5SOS's Michael Clifford and Luke Hemmings during a backstage interview at the American Music Awards.
The 22-year-old heartthrob stormed in on 5SOS post performance interview with Sugarscape and said: ''I just thought I'd come say hello.''
Luke, 19, remarked: ''You look a little drunk''.
The 'Drag Me Down' singer then asked the 5SOS boys: ''Are you drinking without me boys? Can you not wait?''
Niall said: ''It was Mikey's birthday the other day. We all hung out. We all love each other.''
Mikey - who had recently celebrated his 20th birthday - added: ''We all touched butts.''
While Luke shared: ''We had some intimate moments.''
Niall then left the boys to complete the interview and got ready for One Direction's rendition of 'Perfect'.
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